NASA, which plans to send a manned Mars mission by 2031, didn't immediately react to the ambitious timeline set by Rep. Lamar Smith (R-Texas), and experts present at the hearing said that everything would have to go exactly according to plan to meet that deadline.

"We are not the only nation interested in extending humanity's reach into the solar system," Smith said at a hearing Thursday. "One of the three major space-faring nations will reach Mars first. The question is whether it will be the U.S. or China or Russia."

One of the reasons why 2021 will be a good time to launch a Mars mission is because Earth and Mars will be closely aligned, cutting in half the three-year journey and saving fuel. The next time the two planets will be similarly aligned is in 2031, hence the selection of that date by NASA.

It would heavily depend on the progress of the Space Launch System (SLS) rocket and Orion multi-purpose crew vehicle that NASA is developing for its manned Mars mission. Experts said that other issues like space radiation, life-support systems and propulsion still need to be fully addressed before undertaking such a mission.

But others on the panel chose a conservative approach to launching a flyby mission.

"I doubt that a flyby of Mars will ultimately be considered to be an appropriate first shakedown of a flight for a new crewed spacecraft, given the risk involved," said Rep. Eddie Bernice Johnson of Texas, the top Democrat on the panel.

Republican Rep. Dana Rohrabacher of California referenced American financier Dennis Tito's announcement Thursday that he had cancelled plans to launch a manned mission to Mars as early as 2018.

Tito said that after reviewing his plans with NASA centers and other academia, he realized that the "most practical and beneficial approach for America's space program would be to use the NASA Space Launch System and Orion crew vehicle for a similar window of opportunity."

Rohrabacher said that it was becoming increasingly difficult for NASA to attempt such mission given budget constraints and proposals from private groups to launch their own missions to the Red Planet.

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